Ebola virus disease (EVD; formerly known as Ebola haemorrhagic fever) is caused by infection with Ebola virus which belongs to the family Filoviridae. EVD in humans has an average case fatality rate of around 50% (varied from 25% to 90% in previous outbreaks).
EVD first appeared in 1976 in South Sudan and the Democratic Republic of the Congo, the latter in a village situated near the Ebola River, from which the disease took its name. The disease has appeared sporadically since then. Confirmed cases of EVD have been reported mainly in sub-Saharan Africa including the Democratic Republic of the Congo, Gabon, South Sudan, Cote D'Ivoire, Uganda and Congo.
The EVD outbreak which occurred in West Africa from March 2014 to January 2016 was the largest outbreak since Ebola virus was first discovered in 1976. It affected mainly Guinea, Liberia and Sierra Leone. In August 2018, an EVD outbreak was reported in the Democratic Republic of the Congo, with more than 3000 cases reported by October 2019.
EVD is a severe acute viral illness often characterised by sudden onset of fever, intense weakness, muscle pain, headache and sore throat. This is followed by vomiting, diarrhoea, rash, impaired kidney and liver function, and in some cases, both internal and external bleeding.
Mode of transmission
Ebola virus is introduced into the human population through close contact with the blood, secretions, organs or other body fluids of infected animals. Some fruit bats are considered to be the natural host of Ebola virus. In Africa, infection has been documented through the handling of infected chimpanzees, gorillas, fruit bats, monkeys, forest antelope and porcupines found ill or dead in the rainforest.
It then spreads in the community through human-to-human transmission, with infection resulting from direct contact (through broken skin or mucous membranes) with the blood, secretions, organs or other body fluids of infected people, and indirect contact with environments contaminated with such fluids.
People are infectious as long as their blood and secretions contain the virus. Burial ceremonies in which mourners have direct contact with the body of the deceased person can also play a role in the transmission of EVD. Healthcare workers in affected countries have frequently been infected through close contact with patients suffering from EVD when infection control measures are not strictly practised. Samples from patients are biohazardous and testing should be conducted under appropriate biological containment conditions.
Although rare, sexual transmission of Ebola virus has been reported. Based on current evidence, World Health Organization (WHO) recommends that survivors of EVD and their sexual partners should either abstain from all types of sex, or practise safe sex through correct and consistent condom use for 12 months from onset of symptoms or until the semen tests negative twice for Ebola virus.
It ranges from 2 to 21 days.
There is no specific treatment for the disease.
Patients must be managed in isolation facilities to prevent the spread of infection. Severely ill patients require intensive supportive care. Patients are frequently dehydrated and require oral or intravenous rehydration.
Healthcare workers should put on personal protective equipment and adopt strict infection control measures when caring for suspected patients.
There is currently no registered vaccine for EVD in Hong Kong. An Ebola vaccine, called rVSV-ZEBOV, was shown to be highly protective against the deadly virus in a major trial led by WHO in Guinea in 2015.
To prevent the infection, it is important for travellers who go to affected areas to observe the following:
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